Roll embossing of discrete features

Abstract

A cold rolling process for impressing a pattern on a surface of a sheet metal article involves passing the sheet article through a pair of rolls and engaging a patterning feature with isolated areas of a surface of the sheet article, at a localized pressure to plastically deform at least the surface of the sheet article. A rolling pressure is maintained on other areas of the sheet article that is less than the bulk elastic yield strength of the metal. A cold rolling apparatus is also described having a pair of rolls, each with partially cylindrical outer surfaces. The rolls have a gap between the cylindrical parts. One of the rolls has a localized surface region that is displaced relative to the surface of the roll. When the localized region is brought near the other roll, a spacing exists that is narrower than the gap. One of the rolls has a localized patterning feature that aligns with the localized surface region to impress a pattern into the sheet article. The gap allows the rolls to engage opposite surfaces of the sheet article while imparting compression less than a bulk elastic yield strength of the metal.

1. A cold rolling apparatus for impressing a pattern on a surface of a sheet article made of a predetermined metal, said apparatus comprising:
 a. a pair of rolls each having an outer surface that has a cylindrical part, said rolls being disposed with a gap present between said cylindrical parts of said rolls; 
 b. one of the rolls of said pair having a localized surface region that is displaced by at least 5 microns relative to the cylindrical part of said roll such that, when said localized region is brought into proximity with the other roll of said pair, a spacing exists therebetween that is narrower than said gap; and 
 c. one of said rolls of said pair having a localized patterning feature to be impressed on the surface of said sheet article, said localized patterning feature being aligned with said localized surface region, at least when engaging said sheet article, for impressing said pattern into the surface of said sheet article; 
 wherein the gap is of a width effective to cause the cylindrical parts of said rolls to engage opposite surfaces of the sheet article while imparting compression less than a bulk elastic yield strength of said metal. 
 
     
     
       2. The apparatus of  claim 1  wherein the localized surface region is formed by a method selected from the group consisting of selective back polishing, grinding, rotogravure printing, photoresist, optical masking and etching. 
     
     
       3. The apparatus of  claim 1 , wherein said localized surface region and said patterning feature are both present on one of said pair of rolls, with said patterning feature forming at least part of an outer surface or outline of said localized region. 
     
     
       4. The apparatus of  claim 1 , wherein said localized surface region is formed on one of said pair of rolls and said patterning feature is formed on the other of said pair of rolls. 
     
     
       5. A cold rolling apparatus for impressing a pattern on a surface of a sheet article made of a predetermined metal, said apparatus comprising:
 a. a pair of rolls each having an outer surface that has a cylindrical part, said rolls being disposed with a gap present between said cylindrical parts of said rolls having a width effective to cause the cylindrical parts of said rolls to engage opposite surfaces of the sheet article while imparting compression less than a bulk elastic yield strength of said metal; 
 b. one of the rolls of said pair having a localized surface region that is displaced relative to the cylindrical part of said roll such that, when said localized region is brought into proximity with the other roll of said pair, a spacing exists therebetween that is narrower than said gap; and 
 c. one of said rolls of said pair having a localized patterning feature to be impressed on the surface of said sheet article, said localized patterning feature being aligned with said localized surface region, at least when engaging said sheet article, for impressing said pattern into the surface of said sheet article; 
 wherein one of said pair of rolls has a projection from its cylindrical part and the other of said pair of rolls has a recess in its cylindrical surface, said projection and said recess being shaped and dimensioned so that said projection extends across said gap into said recess when said rolls are rotated to bring said projection and recess into alignment, in which orientation said projection and recess having confronting ends that are separated by said spacing that is narrower than said gap, with said patterning feature being present on at least one of said confronting ends. 
 
     
     
       6. The apparatus of  claim 5  wherein the projection and the recess are macroscopic in depth and wherein the confronting ends are macroscopic in area.